From: =?ISO-8859-15?Q?Luk=E1=A8_Czerner?= <lczerner@redhat.com>
Subject: Re: [PATCH 01/15 v2] mm: add invalidatepage_range address space
 operation
Date: Wed, 5 Sep 2012 12:42:54 -0400 (EDT)
Message-ID: <alpine.LFD.2.00.1209051234570.18459@new-host-2>
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 <20120905155648.GA15985@infradead.org>
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Cc: Luk?? Czerner <lczerner@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
        tytso@mit.edu, hughd@google.com, linux-mm@kvack.org
To: Christoph Hellwig <hch@infradead.org>
Return-path: <owner-linux-mm@kvack.org>
In-Reply-To: <20120905155648.GA15985@infradead.org>
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On Wed, 5 Sep 2012, Christoph Hellwig wrote:

> Date: Wed, 5 Sep 2012 11:56:48 -0400
> From: Christoph Hellwig <hch@infradead.org>
> To: Luk?? Czerner <lczerner@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>, linux-fsdevel@vger.kernel.org,
>     linux-ext4@vger.kernel.org, tytso@mit.edu, hughd@google.com,
>     linux-mm@kvack.org
> Subject: Re: [PATCH 01/15 v2] mm: add invalidatepage_range address space
>     operation
> 
> On Wed, Sep 05, 2012 at 10:36:00AM -0400, Luk?? Czerner wrote:
> > However if we would want to keep ->invalidatepage_range() and
> > ->invalidatepage() completely separate then we would have to have
> > separate truncate_inode_pages_range() and truncate_pagecache_range()
> > as well for the separation to actually matter. And IMO this would be
> > much worse...
> 
> What's the problem with simply changing the ->invalidatepage prototype
> to always pass the range and updating all instances for it?
> 

The problem is that it would require me to implement this
functionality for _all_ the file systems, because it is not just
about changing the prototype, but also changing the implementation to
be able to handle unaligned end of the range. This change would
involve 20 file systems.

It is not impossible though... so if people think that it's the
right way to go, then I guess it can be done.

-Lukas

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